False-twist textured synthetic filament yarn is manufactured with a false-twist texturing machine which heats finish-applied synthetic filament yarn with its heating device, and then processes the yarn in simultaneous twisting and drawing with its false-twisting device. False-twist texturing machines fall into two types; a non-contact heating type which heats synthetic filament yarn with radiation heat from a high temperature heater (hereinafter referred to as a non-contact type false-twist texturing machine), and a contact heating type which heats synthetic filament yarn being contacted on a heater (hereinafter referred to as a contact type false-twist texturing machine).
A non-contact type false-twist texturing machine is apt to result in broken filaments and ends down due to its high-speed false-twist texturing operation. The major cause of the broken filaments and ends down in a process with a non-contact type false-twist texturing machine is the load given to synthetic filament yarn in high-speed drawing and false-twist texturing, because such load increases breakage of monofilaments.
On the other hand, a contact type false-twist texturing machine has been increasingly employed for processing various yarns along with the recent diversification in false-twist textured yarns represented by fine-denier yarns, full-dull polymer yarns, yarns of modified cross sections, and yarns spun of multicomponent polymer, all of which are applied with higher amount of finishes or apt to generate fiber waste in texturing so as to increase broken filaments and ends down. Those yarns also shorten the cleaning intervals for heaters of texturing machines to hinder high-speed texturing operation. Broken filaments and ends down in texturing with a contact type false-twist texturing machine are also caused by the load given to synthetic filament yarn of low monofilament tenacity that accelerates breakage of monofilaments. One of the causes of the load given to synthetic filament in texturing process is stain on heater surface resulted from finishes and fiber waste.
For solving these problems, several methods (for example, those in Patent References 1 to 4) have been suggested. Those methods provide finishes applicable to yarns to be textured with both contact and non-contact type false-twist texturing machines, and the finishes contain fluorine compounds which function to decrease the surface tension of the finishes in a specified temperature range so as to prevent broken filaments and ends down. Another method for solving the problems (for example, the method in Patent Reference 5) provides a finish which is formulated by combining a polyether and ether ester each having a M.W. in a specified range and attains stable false-twist texturing to decrease broken filaments. Furthermore, finishes containing polyether compounds and specific polyorganosiloxanes (for example, those in Patent References 6 and 7), and a finish containing a secondary alcohol or its derivative (for example, that in Patent Reference 8) have been suggested for texturing with a contact type false-twist texturing machine.
The fluorine compounds in finishes disclosed in Patent References 1 to 4, however, excessively decrease the surface tension of finishes to cause finish emulsion to be thrown off from yarn and result in insufficient amount of finish on yarn so as to fail to sufficiently prevent broken filaments and ends down. In addition, the fluorine compounds increased the cost of the finishes to disturb their practical use. Furthermore, the finishes containing the fluorine compounds could not sufficiently prevent broken filaments and ends down in texturing with a contact type false-twist texturing machine, because the fluorine compounds in finishes evaporated on the heater plate of a contact type heater before the compounds exert their effect.
The method in Patent Reference 5 failed to uniformly coat filament surface, and resulted in insufficient filament cohesion which leads to varied yarn tension in false-twist texturing, broken filaments, and ends down.
Finishes represented by those disclosed in Patent References 6 and 7 could not decrease stain on heater surface which was caused from finishes thrown off from filament yarn in false-twist operation to be stuck on heater surface, and resulted in broken filaments and ends down due to the stain. A finish represented by that disclosed in Patent Reference 8 formed weak finish film on filament surface to attain poor filament cohesion, and could not sufficiently prevent broken filaments and ends down.
Those finishes seriously decreased their flowability at the initial stage of heating yarn on heater surface (for example, the finishes in Patent References 1 to 5 and 8), or left hard finish residue on heater surface due to the increased amount of finish accumulated on heater surface for a long term of texturing (for example, the finishes in Patent References 6 and 7) so as to fail to sufficiently prevent broken filaments and ends down. Some finishes exhibiting good flowability at the initial stage of heating left high amount of finish residue on heater surface and failed to sufficiently prevent stain on heater surface.    [Patent Reference 1] JP A 2003-213571    [Patent Reference 2] JP A 2004-124354    [Patent Reference 3] JP A 2000-080561    [Patent Reference 4] JP A 2004-124354    [Patent Reference 5] JP A 08-325949    [Patent Reference 6] JP A 10-131055    [Patent Reference 7] JP A 10-072783    [Patent Reference 8] JP A 2003-313773